Treatment of drilling fluids



eo zsm muss mum's or panama rsmns Truman 3. Wayne. Houston. Tel- No Drawing.

on March 81, .1883,

Applies Serhi N0. 71,17

14 Clam. (CL 252-85) Thisinventionrelatesgenerallytowelldrilling and particularly to the treatment of drilling fluids or mud which are circulated in the bore hole in theprocessofrotarydrilllng. Astocommon subject matter this application is a continuation in'psrt of my prior copending application Serial No. 24,083, flled May 29, 1985.

In the practice of rotary drilling, such as is carnedoutinthedrillingof-oilandgaswells, a mud or clay laden fluid is circulated in the bore hole in order to remove the cuttings and accomplish other purposes. Such a drilling fluid may contain, in addition to water, a solid component such as a drilling clay, bentonite, etc., including a Bel-forming component. As the drilling progresses and the hole is made, strata of various formations are encountered and consequently the mud may become contaminated with various constituents which do not readily deposit in the settling ditches. Some of these tlons through which the drilling is progressing may themselves have the eifect of increasing the viscosity of the mud, while others may have the effect of neutralizing such viscosity reducing agents as may have been added to the mud.

Various agents have heretofore been employed for reducing the viscosity of the mud employed in rotary drilling, but in most instances it has been necessary to continuously add such viscosity reducing agents to the mud as it is continually recirculated through the bore hole. This is possibly due to the fact that constituents taken up from the formation and retained in the mud have a neutralizing influence upon the viscosity reducing agents heretofore employed and consequently the viscosity reducing agents must be continuously applied, not only to fresh mud but to previously treated mud as well.

The obj ct of the present invention, generally stated, is to provide in the treatment of a well drilling fluid or mud, a mud treating agent having improved characteristics and particularly one which is more eflicient in reducing the viscosity of the mud than those heretofore employed.

Another object of the present invention is to provide in such treatment, a mud treating agent capable of reacting with the alkaline earth constituents taken up from the formation and producing colloidal compounds thereof under conditions such that they have little or no influence upon the characteristics of the mud.

A more speciflc object of the invention is to provide in such treatment. a mud treating agent ganio protectives heretofore used in this connection are activated and maintained active to an extent such as to'improve their eiiiciency.

Other oblects will become apparent to those skilled in the art when the following description isread.

In accordance with the present invention a mud treating agent is provided and employed which has the chest of activating the feeoly acid organic compounds, such as numic acid compounds, present in all surface clays and in many clays of deeper formation as well as upon such feebly acid organic compounds or the commonly used protectives which may have been naturally or artificially introduced into the mud. Such activation increases the activity of these protectives at the surface of the gel particles in the mud and enhances the well known protective influence of this class of organic substances.

:0 Moreover, the present invention contemplates constituents which are taken up from the formae the use of a mud treating agent containing a radical which will react with calcium, magnesium. iron and aluminum salts so as to produce colloidal reaction products. The present invention as particularly contemplates a mud treating agent containing a phosphate radical in such condition that, while the compound is available for reaction with the alakaline earth salts, which may have been taken up by the mud, in orderto neutralize their influence upon the mud, the compound is, nevertheless, one which accomplishes this result without, at the same time, substantially altering the pH value of the mud. For example the metaphosphorlc acid radical produces advantageous results when used as a mud treat ng a ent. The metaphosphoric acid radical apparently activates such organic protectives as may be present naturally or artificially in the mud to such an extent that the latter are considerably more eflective in reducing the viscosity of the mud, both initially and after the mud has been in use for several hours, than would otherwise be the case. For instance, an admixture of sodium hexametaphosphate and a suitable tannin compound is considerably more eflective, both initially and after the mud has been in use for several hours than a corresponding mixture in which mono or disodium-orthophosphate has been used instead of the metaphosphate. This diflerence in efiiciency is particularly noticeable when the drilling fluid contains muds derived from calcareous shales. The metaphosphate should have the property of acting as a viscosity-reducing agent when adder. to a drilling fluid or mud and should of the type referred to in which the common ortherefore be sufliciently soluble in the fluid under the conditions encountered in well drilling to accomplish that result.

Metaphosphoric acid and its salts and esters with hydroxy compounds oi the tannin type produce particularly advantageous results. This may be attributable to the iact that metaphosphoric acid compounds may be ieebly acidic when first introduced into the mud, and the phosphate radical or even the carbonyl or phenyl radicals present in the composition or which become available through hydrolysis or ionization may react with the alkaline earth constituents present in the mud. This reaction is accomplished without substantial variation oi the pH value oi the mud. as the reagents themselves do not depend on the deiiocculating action oi iree alkali and thus obviate the swelling and hydration oi the clay particles which almost invariably iollows the use oi alkaline treating agents, or those which liberate alkaline sodium compounds in their reactions with the alkaline earth constituents oi the mud. The use oi a strongly acid compound, unless used in an amount suilicient to denature most oi the colloids oi the mud, would cause flocculation and thickening.

In the case of the esters oi acid and hydroxy carboxylic acids such as as gallic, and the like, it is possible that the alkaline earth constituents in the mud react with the carboxyl group or its soluble sodium, ammonium, or hydroxyamine salts.

With the pH value oi the mud maintained substantially constant, notwithstanding the reactions which may be going on to neutralize the eiieot oi the alkaline earth constituents taken up by them, the eiiect oi the usual organic protectives present, naturally or artificially, in the mud is unmitigated.

The sodium metaphosphate oi commerce is suitable ior use in accordance with the present invention, notwithstanding the iact that some grades may contain added sodium carbonate or trisodium phosphate. The sodium metaphor phate employed may be one consisting largely oi the hexa-polymer but containing small percentases oi sodium pyrophosphate produced as a byproduct during manuiacmre or which may have been added to adjust the pH value oi the commercial product. Metaphosphcricacid in anhycirous iorm may be employed but, due to the diiilcuities in preventing hydration oi this material, it is more convenient to employ a compound thereoi.

The esters oi metaphosphoric acid are particularly well suited ior usd in accordance with the present invention. These esters may be prepared by first isolating the ireo metaphosphoric acid in any suitable manner and then esteriiying the anhydrous or nearly anhydrous iree acid with an organic hydnoxy body by any oi the well known procedures used in the preparation oi orsanic esters. The acid and organic hydroxy body may, ior instance, be esteriiled by heating them ior several hours below the decomposition point oi the hydroxy bodies employed and a suitable catalyst may be employed to hasten the reaction. I! desired, dry hydrogen chloride gas may be passed through the reaction mixture to accelerate the ester-location and carry it more nearly to completion. Suitable inert solvents may also be employed ior expediting the reaction and in iact anyoitheexpedientsocouringtothcseskiiled in the art oi organic reactions and synthesis may be employed.

droxy phenols which are amphoteric in nature, such as pyrogallol, resorcinol, phloroglucinol, hydroxyquinol, and catechol; esters. glucosides, and anhydrous salts oi gallic, protocatechuic, digallic, ellagic, and similar polyhydroxy aromatic acids having iree hydroxy groups, are particularly suitable ior use in accordance with the present invention. Esters oi metaphosphoric acid with iully soluble polyhydric alcohols such as glycerol, glycol. and arabitol are suitable but the esters oi metaphosphoric acid with tannins and tanninlike bodies commend themselves as more desirable irom a practical standpoint.

While the mud treating agents oi the present invention may be applied to the mud in a dry condition, it is ordinarily more convenient to apply them in a convenient solution which may be added to the mud at a suitable point in the circulatory system. For instance, the treating agent may be added to the mud in the usual ditch lust beyond the point where mud irom the well is discharged or at any other suitable point beiore the mud reaches the suction pumps which return the stream to the bore hole. Frequently, however, it is advantageous to admit the treating agent directly into the pump suction as very eflicient mixing is accomplished in this manner.

As a specific example illustrating the use of the treating compounds in accordance with the present invention, sodium hexametaphosphate may be used. For instance, ten pounds of a dry mixture prepared irom nine parts oi powdered sodium hexametaphosphate and one part of soda ash may be dissolved in ility gallons of water. This solution may be slowly ied into the mud in such manner that the entire amount or treating agent has been introduced into the mud by the time iirst returns oi treated mud reach the point oi application. The quantity stated in this example is adequate ior the treatment oi 250 barrels oi drilling mud with the result that the viscosity oi mud was reduced irom 57 centipoises (beiore treatment) to 26 centipoises (aiter treatment).

The mixture just described was employed in the treatment oi a mud from the Fittstown area oi Oklahoma using two parts oi a 10% solution of the dry mixture, described above, to a thousand parts or mud. The initial viscosity oi the mul was 51.6 centipoises and the viscosity, aiter treatment, was 22.5 centipoises while the gel strength oi the colloidal matter in the mud was greatly reduced.

Another example oi mud irom the Fittstown area oi Oklahoma which had been previously untreated was treated with two parts per a thousand 0! a 10% isopropanoi solution oi an ester prepared irom molecular proportions oi phosphorus pentoxide and sodium tannate. The initial viscosity oi 61.6 centipoises was thereby reduoed to 24.0 centipoises.

The mud last mentioned is illustrative or one in which satisiactory results have not been obtainable will the usual alkaline caustic soda and tannin mixtures or mixtures oi these with other customary materials.

As a iurtber example illustrating the eiiect oi the compounds oi the present invention upon a ten pound mud prepared irom corings derived irom the Yegua shale iormation oi the Texas Gulf coast area, such a mud was treated with an ester prepared irom three molecules oi anhydrous metaphosphoric acid and one molecule oi the anhydrous sodium salt oi gallic acid. This agent also used as a 10% alcoholic solution in Esters oi meta-phosphoric acid with poly-hyre the proportion oi two parts ior each thousand ass-mos parts of mud. The initial viscosit! of 57 centipoises was reduced to 26 oentipoises by this treatmerit. a

While in the foregoing'specifio examples the eflect of the treating agents of the present invention used alone has been illustrated, it will be understood that-other mud treating agenu heretoiore employed and having a particular eifect upon the mud in be employed together with the compounds of the present invention. For instance, alkaline sodium tannates, sodium orthophosphates, sodium silicates, etc. which have a buffering action may be used together with the compounds of the present invention. In most instances, however, due to the relatively small amounts of the treating agents of the present invention required to produce efilcient results, it is desirable to use the agents of'the present invention unsupplemented by agents such as those Just mentioned.

While in the foregoing disclosure reference-has been made to various theories of action of the compounds contemplated by this invention and the reactions taking place in the mud pursuant to treatment have been referred to, it is to be understood that while the ultimate effect of the compounds has been proved, the specific actions and reactions herein suggested are speculative to the extent that they are not ascertained with certainty, and hence the invention is not to'be interpreted as being limited by any theoretical consideration or action as herein suggested for the purpose of facilitating an understanding of the disclosure.

From th'foregoing description it is apparent that the present invention accomplishes its objects and provides a treatment for drilling muds in which smaller quantities of the agent are necessary to produce the desired eifect than of those agents heretofore employedfor this purpose and that the effect of the agents of the present invention is a prolonged eifect as distinguished from the more or less temporary effect of the agents heretofore used.

While in the foregoing disclosure of the present invention reference has been made to various specific examples of the mud treating agents in accordance with the present invention, it is not to be understood that the present invention is limited to those particular agents and combinations of agents herein specifically described, but on the contrary the features of the present invention may be applied generally and various modifications may be made in the formulae without departing from the spirit of this invention. It is to be distinctly understood, therefore, that such modifications and the use of such individual features and subcombinations of features as present themselves to those skilled in the art without departing from the spirit of this invention are, although not specifically described herein, contemplated by and within the scope of the appended claims.

Having thus described the invention what is claimed is:

agent containing the metaphosphate radical and an organic protective compound.

4. In the art of drilling and controlling wells in which mud. containing hydrated ay colloids, organic protective compounds, and mineral salts. the process of reducing viscosity of the mud, comprising, treating the mud with an agent containing reactive metaphosphate-radical.

5. In the art of dril ng and controlling wells in which mud is circulated in the bore hole, the process comprising, treating the mud with sodium metaphosphate.

6. A drilling mud comprising clay, water, an alkali metal hexametaphosphate, and a lyophile colloid.

'7. A drilling mud in the form of a thixotropic dispersion comprising clay, water and an alkali metal hexametaphosphate in small amount sufficient to render the drilling mud substantially immune to deterioration by base exchange,

8. The method of substantially immunizing a thixotro, J drilling mud against deterioration by base exchange which comprises adding thereto an alkali metal hexametaphosphate.

9. A- method of maintaining the thixotropic character of a drilling mud containing bentonite clays, which comprises adding thereto an alkali metal hexametaphosphate.

10. A method of converting a drilling mud comprising a dispersion of a hentonlte clay in water calcium, magnesium and other metal salts dis-' solved therein are immediately locked into a soluble, substantially non-ionized condition.

14. In the drilling of oil and gas wells, the steps in controlling the gelation and viscosity of the drilling mud which comprises adding thereto sodium poly-metaphosphate.

. TRUMAN B. WAYNE.

- caamxcim or ':ommcr1on. Patent No- 2J8'b69 h October 25, l9h5. I TRUMAN B. WAYNE.

It-is hereby certified that error appears in the printed specification of the above numbered potent requiring eorreetionas follows: Page 2, first column,"line 26, for the words "of acid" reed ot metaphosphorie acid--; page 3, second-column, line 23, after metsphosphate. insert the follow- "ing as claim 6 "A drilling mudoomprising a dispersion clay in an aqueous solution of an alkali metal hexametaphosphate.--;

and for the claims non numbered "6, 7', "8", "9", "1O", "11", "'12", "15" and --15-- respectively; in the heading to the printed specification, line 6, for "11;. Claims" read --l5 Claims; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. "5

Signed and sealed this 18th day of December, A. D. 1914.5.

Leslie Frazer (Seal) First Assistant Commissioner of Patents? 

